This invention relates to a new process for the preparation of 1-cyclopropyl-7-substituted-6-fluoro-4-oxo-1,4-dihydro-quinoline-3-carboxy lic acid derivatives and pharmaceutically acceptable salts thereof.
It is known that the 1-cyclopropyl-7-substituted-6-fluoro-4-oxo-1,4-dihydro-quinoline-3-carboxy lic acid derivatives of the Formula I ##STR5## wherein R stands for a piperazinyl, 4-methyl-piperazinyl or 4-ethyl-piperazinyl group possess high antibacterial activity (Eur. J. Clin. Microbiol. 1983, 2, page 111; J. Clin. Pharmacol. 1985, 25, page 82; Drugs Exptl. Clin. Res. 1985, 5, page 317.
The quinoline carboxylic acids of the general Formula I can be prepared by reacting 1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-quinoline-3-carboxylic acid and a cyclic amine in the presence of a solvent at a temperature of 135.degree.-140.degree. C. for 2 hours (German Open Application 3.033.157; German Open Application 3.142.854).